Site-Specific Ir Single Atoms in Spinel Induce 5d Spin Polarization for Enhanced Oxygen Evolution

Area of Science:

• Materials Science
• Catalysis
• Inorganic Chemistry

Background:

• Precise control over single-atom catalyst coordination environments is crucial for understanding structure-activity relationships.
• Tuning local symmetry around single-atom centers influences electronic structure and catalytic performance.

Purpose of the Study:

• To develop a method for selectively embedding single iridium (Ir) atoms into specific crystallographic sites (tetrahedral and octahedral) within a spinel ZnCo2O4 support.
• To investigate how the coordination environment of single Ir atoms affects their electronic structure and oxygen evolution reaction (OER) activity.

Main Methods:

• Li-assisted vacancy engineering to control Ir atom incorporation into ZnCo2O4.
• Theoretical calculations (e.g., DFT) to analyze electronic structure and hybridization.
• Experimental characterization of catalyst properties.
• Electrochemical testing for OER performance and stability.

Main Results:

• Successfully synthesized single-atom catalysts with Ir selectively placed in tetrahedral and octahedral sites of ZnCo2O4.
• Octahedral site incorporation led to significant electronic reconfiguration and spin polarization of Ir atoms due to enhanced Ir-Co-O hybridization.
• This electronic modification optimized binding energetics for oxygen intermediates, boosting intrinsic reactivity.
• Octahedral-site Ir catalysts demonstrated a remarkable OER mass activity (5520 A/gIr at 300 mV), vastly exceeding IrO2, and showed stability over 200 hours.

Conclusions:

• Crystallographic site selection is a key strategy for tuning the electronic structure of 5d single-atom catalysts.
• The coordination environment directly impacts catalytic behavior, offering mechanistic insights into OER.
• This work provides a pathway for designing highly efficient and stable single-atom catalysts through precise coordination control.